Apple IPad Case
I'm not a big fan of Apple accessories in general--they're often more expensive and less functional than those from third-party companies. But the $39 Apple iPad Case is a highly functional case that's also a good value.
The black case, made of a soft and light wetsuit-like material, benefits from Apple designers having had plenty of time to spend with the iPad and think about how people would use it. The front of the case is stiff but hinged, offering some small amount of screen protection and foldability. The back side is softer, but the iPad's aluminum back provides the structure there. Sliding the iPad into the back side of the case, and then folding down a flap of material to secure the device in place, can be a struggle at first, though I found that the case loosened up over time. (Thankfully, because with the case on, you can't use the iPad in a dock.) The case material is quite light, however, so it doesn't add much bulk compared to similar cases I tried.
The iPad can be a little slippery by itself, but the iPad Case's texture makes the iPad easier to grip with one hand; I found myself often sliding my index finger inside the case while reading to get an even stronger grip. And a strange little flap on the case's backside allows you to wrap the case's front side around and secure it in place, giving the iPad a slight incline on your lap or a table to aid in typing or, flipped around, allowing you to stand it upright on any flat surface. I use these features all of the time--the iPad Case has definitely increased my enjoyment of the iPad.
The case isn't without its flaws. The material picks up dust and crud all too easily, so it rapidly ends up looking more well-loved than immaculate. The case's edges are a bit sharp, though after a few days of use they'd been flattened out enough that I rarely noticed. And while the big Apple logo on the front might make some people proud to flash that well-known brand, I'd actually prefer something a bit more understated.
No doubt there's a better iPad case out there, somewhere, waiting to be invented. But in the meantime Apple's own case is the most versatile and useful I've seen, so long as you don't mind some schmutz and a big logo.